Normally, automobile bodies are configured from a portion formed by resin components such as bumpers (hereinafter referred to as “resin part”), and a portion formed by steel sheet components such as the body (hereinafter referred to as “steel sheet part”). Herein, there is concern over the resin part deforming when baking, in the case of coating a coating of high baking temperature onto the resin part, since the heat resistance of resin components are greatly inferior compared to steel sheet components. For this reason, it is common practice to coat a suitable coating at suitable coating conditions on every respective part.
However, when coating different coatings on every respective part, deviation in hue occurs, and appearance of the automobile may decline. Therefore, development of a coating that can simultaneously coat both parts among a resin part and a steel sheet part, and nevertheless be of low-temperature curing type has been demanded.
For example, a technology for coating a water-based base coating containing melamine resin and emulsion resin obtained by emulsion polymerizing an ethylenically unsaturated monomer mixture containing methacrylic acid ester, and then coating wet-on-wet a clear coating with isocyanate as a curing agent (refer to Patent Document 1). According to this technology, it is said to be possible to form a coating film superior in low-temperature curability and well as being superior in adhesiveness, even in a case of simultaneously coating both parts among the resin part and steel sheet part.
In addition, as a low-temperature curing coating, for example, a clear coating for automobile bodies containing predetermined amounts of acrylic polyol, blocked isocyanate and melamine resin (refer to Patent Document 2), a top-coat coating for automobile bodies containing predetermined amounts of acrylic polyol, alkoxysilane and blocked isocyanate and melamine resin (refer to Patent Document 3), a water-based heat curable coating for automobile bodies containing predetermined amounts of acrylic polyol, blocked isocyanate and melamine resin (refer to Patent Document 4), etc. have been proposed.
[Patent Document 1] Japanese Unexamined Patent Application, Publication No. 2005-787
[Patent Document 2] Japanese Unexamined Patent Application, Publication No. H10-101995
[Patent Document 3] Japanese Unexamined Patent Application, Publication No. H10-88010
[Patent Document 4] Japanese Unexamined Patent Application, Publication No. 2001-139879